Transmission system



June 10, 1930. F, J. SINGER 1,762,279

TRANSMISSION SYSTEM Original Filed May 4, 1928 INV ENTOR EJSu/z er ATTOR N EY Patented Julie :10, 1930 UNITED STATES PATENT OFFICE FRED J. SINGER, OFROCKVILLE CENTER, NEW YORK, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK TRANSMISSION SYSTEM Original application filed May 4, 1928, Serial No. 275,165. Divided and this application filed August 15,

1929. Serial This invention relates to telegraph transmission, receiving and signaling systems. More particularly, this invention relates to arrangements for converting pulses or pulsations of alternating current into corresponding direct current pulses or pulsations. Still more particularly, this invention relates to arrangements interconnecting an alternating current relay, the winding of which is energized with pulses or pulsations of alternating current, and a direct current relay, the armature of which is to control the operation of a telegraph line or other signaling circuit so that pulses or pulsations of direct current may be transmitted over the telegraph line or other signaling circuit in accordance with the pulses or pulsations of alternating current energizing the winding of the alternating current relay.

This is a division of a copending applica tion, Serial No. 275,165, filed on May 4, 1928.

Heretoforc, pulses or pulsations of alternating current, which may be characteristic of telegraphy, or ofv other'signals, were transmitted over an electrical circuit, one of these pulses or pulsations representing, for example, a marking signal, and the absence of that pulse or pulsation, a spacing signal. At the distant or receiving terminal of the system, an amplifier, frequently of the vacuum tube type, was employed for the purpose of amplifying these alternating current pulsations. Coupled to the amplifier there was a detector, frequently also of the vacuum tube type, this detector being employed to rectify the re ceivcd and amplified pulsations and to trans form these pulsations into corresponding direct current pulsations. It was also the practice to so relate a direct current relay to the output of the detector or rectifier that the armature of this relay might move back and forth between its contacts and thereby control and operate another electrical circuit, which may, for example, be a telegraph loop. Such an arrangementis well known to be quite expensive in its first cost as well as in its operating charges. It is proposed to substitute for the amplifier. detector or rectifier, etc., a relay system which may include an alternating current relay upon the winding of which may be impressed high frequency signals which may be merely alternating current pulsations, and a direct current relay properly related and connected to the alternating current relay, so that the armature of the direct current relay may control the operation of another circuit which may be the above mentioned telegraph loop.

Thus, it is one of the objects of this invention to provide a receiving circuit for receiving and/or detecting modulated high frequency signals substantially without distortion and not necessarily including vacuum tube circuits.

Another of the objects of this invention is to properly interconnect a tuned, sensitive alternating current relay which may be energized by alternating current pulses, and a direct current relay .contolling a receiving circuit, so that the direct current relay may control. the transmission of pulses of direct current to the receiving circuit corresponding to the impressed alternating current pulses.

A further object of this invention is to provide a receiving circuit which may include a direct current relay, the windings of which may become energized by low voltage currents, which may be signaling currents, and the armature of which may control the transmission of higher voltage currents to the re ceiving circuit, or conversely, a similar arrangement may be employed in which the voltages of the respective currents are inverted in their relative magnitudes.

And it is a still further object of this invention to combine an alternating current relay, the armature of which may vibrate at a definite periodicity when alternating cur rent of corresponding frequency is impressed upon the Winding of that relay, and the armature of which is to remain fixed against one of its contacts when no current is impressed upon the winding of the relay, with means to prevent the armature of that relay from remaining connected with one of its contacts for a prolonged period of time when alternating current of the desired frequency is energizing that relay. Thus, a receiving relay may be so related to the system that its nals which may be modulated upon carrier vibrates iniaccordance withthe signals repre\ ti P2 I sented by the alternating current pulsatlons;

and Fig. 2 represents a modification of the arrangement shown in Fig 1.

Referring to the drawing, L deslgnates an electrical circuit over which may flow al ternating current pulsations. These alternating current pulsations may, for example,- be produced by an alternating current genfilterv of the type disclosed in Campbell Pat erator, the output of which is interrupted at more or less regular intervals so that these pulsations may .be characteristic of signals such as are employed in telegraph signaling systems. These pulsations may become impressed upon a filter F, which may be of any well-known type, preferably a band pass ent 1,227,113, dated May 7 1917. Thus, this band pass filter may freely transmit alternating current, or currents, of frequencies which are quite close to the frequency of the generator employed at. the transmitting terminal of the system. -It will be understood, however, that in practice the employment of the filter may not be deemed necessary, and this is especially so. if the alternating current relay receiving the alternating current pulsations is tuned to the particular frequency of the generator. q

' The filter F is connected to a potentiometer P so that the voltage of the current transmitted thereby may be controlled as found necessary. These pulsations are then impressed upon the winding of an alternating current relay R the armature of which may vibrate .substantially in accordance with the frequency of the current'of each pulsation,

this current being frequently designated carrier current. Relay R 'is preferably a highly tuned polar relay. Its armature may preferably be biased against its'contact. Thus, this armature may be made to normally close its contact by attaching a spring, for example, thereto, or it may be biased magnetically or electromagnetically, or gravitationally due to its weight, or in any other well-known" manner.

W which'may form part of a so-called vibrating circuit. It will be apparent thatthe windings of the direct current-relay may be coupled to one another so that'the'magnetic field established by the current fflowing through these windings may tend to move the armature of the direct current relay back and forth between its contacts S and M. A battery B may be employed to energize the operating windin s of the direct-current relay. In series with %attery B there is the resistance element of a potentiometer P so arranged that the entire battery potential is impressed u'pon'the terminals of the potentiometer, The slidable contact of potenmay be manipulated so as to make any portion of the potential of battery B :available. Accordingly, the magnitude of the potential to be impressedupon the operating windings of the direct current relay and upon the armature and contact ofthe alternating current relay. may be decreased to any desiredvalue. A choke coil K is interposed between the slidablecontact of the potentiometer P and the contact of the armature of the alternating current relay R 'The operating winding W of the relay R is connected in series with the armature of relay R and its contact aswell'as with a resistance-Z The other of the operating windings W of relay R is connected in series with another resistance Z Thus, the current derived from battery B also flows through the choke coil K and through parallel paths, one of which includeswinding W resistance Z and the armature of relay R and its contact, and the other of which includes the winding W and resistance Z It will thus be apparent that as the armature of relay R vibrates in accordance with the frequency of an impressed carrier current, pulses will be received by the-operating windings W1 and W of the. direct current relay R these pulses corresponding to the number of times the armature of relay R closes its contact and-not necessarily corresponding to the frequency of vibration of the armature. It will also be apparent that windings T and W are preferably oppositely poled so that the magnetic field established by one of these windings may cause .the armature of relay R to move towards one of its contacts, while the magnetic field established by the outer of these windings may cause that armature to move to the other of its contacts. Moreover, the resistances Z and Z may be so proportioned that the magnetic field established by one of the windings is considerably greater than the magnetic field established by the other of the windings, so that when current flows through both windings, the armature of-relay R will be held in position against a particular one of its contacts. For example, resistances Z and'Z may be so proportioned that the ourthrough a resistance Z condenser C and- .rent flowing through the winding W and,

consequently, the magnetic field established thereby, may be twice as great as the current flowing through the winding W and the magnetic field established thereby, and, since the effect of winding W is, therefore, greater than that of W the armature will be caused to close contact S. Obviously, when the armature of relay R does not close its contact, no current will flow through winding W and therefore winding W will efi'ectively cause the armature of relay R to close contact M.

A circuit, which may be a local circuit, a telegraph loop, or any other circuit, is designated by the reference character L This circuit is shown under the control of the armature of relay R Contact M may be connected in series with a battery B through a resistance Z while contact S may be connected through a resistance Z to a battery B" which may be of the same potential as battery B but of opposite polarity. Thus, as the armature of relay R moves back and forth between its contacts, current may flow over L from either of the batteries B or \Vinding W of relay IR may be connected in a so-called vibrating circuit, the operation of which will be described later. This circuit is shownin Fig. lto include windings W and W which may be inductively coupled to each other, and which may form the primary and secondary windings of a transformer, a condenser C and winding W, of relay R Line L is connected to ground winding W It will also be apparent that the potential of battery B may be substantially different from the potential, orpotentials, of batteries B and B" and that the potential of battery B may, if desired, be substantially lower than the potential, or potentials, of batteries B' and B" Accordingly, current of substantially low voltage may flow through the operating windings W and W of relay R and through the armature and contact of relay R while current of substantially higher voltage may be supplied to the line L. It will be understood, however, that the relative magnitudes of these voltages may be reversed so that the voltage of they current flowing through the operating windings of relay R may be higher than the voltage of the current with which line L is supplied.

When a distant station may be sending a specific signal, such, for example, as a telegraph spacing signal, no alternating current will flow through the winding of the relay R so that its armature may close the associated contact. Current will then flow through the windings W and W of relay R this current being derived from battery B the magnitude of the elfective voltage of this current being controlled'by the slidable contact of potent ometer P As has already been stated, the current through winding W which is poled in opposition to winding W will cause the armature of relay R to close its spacing contact S. It will be clear that the resistances Z and Z as well as the resistance a of the potentiometer P may be so proportioned that the voltage across the armature R causing its armature to vibrate t erewith.

As the armature of relay R vibrates, the circuit through winding W may become opened and closed periodically, while the circuit through winding W remains closed. Relay R may be so designed that when current of a particular frequency is impressed upon its winding, its armature may close its associated contact substantially fewer times than the frequency of vibration of the armature. Thus, during the transmission of a marking signal there may be several cycles of carrier current transmitted and the armature of the relay R will vibrate a correspondin number of times. The contact of relay R owever, may be closed only during a small percentage of the time, as stated hereinabove, and, therefore, the average current through winding W may be quite small. Incidentally, the average current through winding W becomes increased because the average potential across I ployed at the distant station to control the transmission of alternating current therefrom, the armature of relay R would close the marking contact M when the distant key were closed, and it would close the spacing contact S when that distant key were opened.

It will be clear that when the armature of relay R closes the marking contact M, this contact remains closed throughout the time that suitable current is impressed upon the winding of relay 3,. At all other times, this armature may close, its spacing contact S.

The choke coil K is so related to, the circuits interconnecting the relays R and R as to damp out any sudden impulse which may be caused by the brief closure of the contact of relay R during its vibrations. Accordingly,

the current through winding W is 'efi'ectively prevented from momentarily becoming large enough to cause the armature of relay R to close its marking contact M.

2 of this invention The arrangement of e circuit interconshows a Wheatstone bri necting the armature of relay R and the oper- 'ating windings W and W5 of relay R The a resistance Z and ground. The other diag-- onal of the bridge includes the armature of relay R its contact and choke coil K. It will be apparent that resistances Z Z5 Z and Z may be so proportioned that w j en the armature of relay R definitely closes its contact, the windings W and W will establish proper magnetic fields to move the armature of relay R 'to its spacing contact S. And when the armature of relay R vibrates, due, for example, to the presence of a suitable pulsation in line L, the armature of relay R may be caused to close its marking contact M.- Thus, the magnetic field established by one of these windings may be stronger than that established by the other when a suitable pulsation is impressed, and, conversely, the magnetic field of the latter winding may be greater than that of the former when no such pul sation isimpressed. It will be understood that while this-Wheatstone bridge arrangement may be balanced so that no current may flow through the diagonal including the ar-' mature of relay R when the armature of that relay is fixed against its contact, this bridge is preferably unbalanced so that an'appreciable current may normally flow through the diagonal including the armature of relay R Another, feature of this Wheatstone bridge arrangement is that'it is designed to limit to a definite value the magnitude of the volta eacross the armature and contact of relay Winding W of relay R is connected in what is known as a vibrating circuit. The

purpose of this circuit is to render the relay more sensitive to currents flowing through windings W and W and to prevent chattering or rebound of the armature when it' vstrikes contacts M or S. In the form of viupon as a result of the flow ofcurrents meaave through windings W and W causing it to strike contact S, current will flow from battery B'- through resistance Z armatureof relay B this current then dividing so that part of it flows through the upperhalf of winding W and resistance Z and so that the' :rest of the current flows through thelower f half of winding W and condenser 0. That current which flows through the upper half -.of W and resistance Z will be in such a direction afs'to set up a magnetic field tending to cause the armature to leave contact S. The initial current flowing through the lower half of winding W and condenser G, however, will be considerably larger than the former current and will be in such a direction as to establish a magnetic field about the lower. half of winding W opposing that field setup by the current through the upper half of the winding W and aiding the efl'ect produced by windings W and W2. The relay armature will-therefore haveless tendency to chatter than would be the case if this so-called fvibrating circuit were not connected.

It is not long before the condenser C be- 7 comes fully charged, whereupon the current as long as the stronger magnetic effect of the currents through windingsW and W2 is malntained, whereby the armature is held against contact S. When the magnetic field caused by the'flow of currents through wind-- ings' W1 and W is reversed, however, due to the action of relay R the armature of relay R will leave contact S more easily than would be the case if the current through the upper half of the winding W and' resistance .Z were not present. By virtue of the presence of the vibrating circuit, and of the action of its winding W3, relay R is made quite-sensltive in its action. d

When the armature of relay R opens contact S in its travel to contact M, neither of the batteries B nor B will be connected to winding W yet due to the charged condition of the condenser C, current will flow through both portions of winding W in the circuit including that winding, resistance Z and ground. A magnetic field will therefore be established by winding W tending to sharply kick. the armature .oif'relay-R toward its marking contact M.

When the armature of relay R finally reaches the marking contact M, as willbe the case when the relay R is properly energized,

current will flow )from battery B' through resistance Z the armature of relay R and contact M and this current will then divide so that partof flows through the upper half inabove.

of winding W and resistance Z the remain- .der flowing through the lower half of winding W and condenser C. The currentthrough the upper half of W and resistance Z will continue to flow as long as the armature of relay R is on contact M. But the current through the lower half of winding W and through condenser C will flow at a diminishing rate until condenser C becomes charged to the potential of battery-B' condenser C being now charged to a polarity opposite to that which itihad when the armature closed contact S. This charging current through condenser G will produce a magnetic field about the lower half of winding W which will aid that established by windings W and -W in holding the armature of relay R against contact M, thereby preventing chatter The current flowing through the upper half of winding W and resistance Z will set up a magnetic field opposing that set 'up around windings W and W and that set up by the lower half of winding W Immediately after the armature closes contact M, however, the current through the lower half of winding W and condenser C will be much larger than that through the upper half of winding W 3 and resistance Z so that at first the effective magnetic field due to winding W will aid the efiective magnetic field established by the currents through windings W and 'W thereby holding the armature against contact After the current charging condenser C has decreased to a value less than that flowing through the upper half of .winding W and through resistance Z the reflective magnetic field about winding W will be reversed and will oppose that field established bywindings W1 and W Then the field of winding W3 will aid that produced by windings W and VV upon a reversal of the magnetic field due to the action of relay R When the armature of relay R again closes its contact, the armature of relay R -w'illpromptly close its contact S in the manner already described here- It is to be noted when the armature of re lay R begins to leave con-tact M, current will flow through both portions of windings W due to the charged condition of condenser O, the magnetic field established by winding W3 tending to sharply kick the armature of relay R against the spacing contact S. When the armature of relay R finally reaches contact S, the cycle of events already described hereinabove will be renewed.

The vibrating .circuit of Fig. 1 operates upon substantially the same principles as those described in-connection with the circuit of Fig. 2; yet, the one shown in Fig. 1 is even more effective due to the presence'of the coupled windings W and W These windings may be employed to boost the efiective voltages so that the movement of the armaturedbetween its contacts may be even more rap1 It will be understood that therelay R of this invention is one having an armature which remains fixed against its contact for its spacing condition and vibrates at a high periodicity for its markingcondition.

It will also be apparent that the combination of the two relay R and R and the associated equipment, may take the place of present vacuum tube amplifier, detectors and direct current relays now employed in telegraph receiving systems for receiving pulsations of alternating current corresponding to telegraph signals. Relay R may be considered to perform'the function of an amplifier and a detector, and relay R may be considered to actin somewhat the same manner as the present direct current relay. The principles of this invention may be employed in the reception of telegraph signals substantially free from distortion.

While this invention has been shown in certain particular embodiments merely-for the purpose of illustration, it will be understood that the general principles of this invention may be applied to other and widely varie d organizations, without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is: n

1. The combination of an alternating current relay, a direct current relay having two operating windings, two resistance elements, the two, operating windings of the direct cur-' rent relay and the two resistance elements forming the four arms of a Wheatstone bridge, a choke coil, the armature of the alternating current relay and the choke coil forming one diagonal of the Wheatstone bridge, and a source of direct current potential forming the other diagonal of the Wheatstone bridge.

2. The combination of an alternatlng current relay, a direct current relay having two v operating windings, an unbalanced Wheatstone bridge having the two operating windlngs of the direct current relay as two of its arms, a choke coil, the armature of the alternating current relay and the choke coil forming one diagonal of the bridge, and a source of direct current potential forming the other August, 1929.

FRED J. SINGER. 

